For many years, the traditional method for well made, waterproof walking shoes has been the machine welted method. The method utilizes an insole with an upstanding wall or insole rib which is positioned about 7/32" from the edge of the insole. During the lasting process, the upper and lining (if the shoe is fully lined) are secured to the insole rib. A strip of leather, vinyl, etc., known as the welt, is then sewn in to combine the welt, upper and lining to the insole rib. After the welt has been sewn in, the sole is stuck to the shoe bottom and is stitched through the welt by means of a lock-stitch machine.
A variety of insole ribs are available. Basically, each of these consists of a fiber core covered with a tape or fabric flanged out at each side to define the rib. The rib is either upright or angled. The attachment of the insole rib to the insole is virtually the same for all types. Originally, the insole rib was applied only to leather insoles but today the insole ribs are attached to a variety of insoles.
The insole rib is coated with adhesive, usually a neoprene, allowed to dry and then stored on a reel. The insole rib is fed from a reel and attached to the insole by a special rib-laying machine which uses a jet of hot air to heat-activate the adhesive immediately prior to the rib being attached by a hammering action. It is essential that the rib be accurately positioned in relation in the insole edge; normally 7/32" from the edge.
The prefabricated rib is essentially a woven textile comprised of either cotton, polyester or polyester cotton fibers, coated on one side with an elastomeric adhesive and formed around slit strips of unsaturated leatherboard or TEXON, a latex rubber saturated paper sheet, type paperboard. In attaching the insole rib to the insole, the rib must make two or three turns including a particularly sharp turn at the toe. The turns result in crimps, bumps or puckers--all of which are objectionable. Currently the insole ribs offered have pinked or cut edges to minimize the problem caused by these turns.
The present invention entails the use of a fabric for an insole rib where the warp and weft threads are arrayed such that when the insole rib is secured to the insole the weave contracts along its inner diameter and expands along its outer diameter while lying substantially in the same plane. Because of this, the insole rib can be made without pinking, although it can also be made with pinking if desired. This results in the insole rib lying substantially flat along its entire length when adhered to the insole.